1. Field of the Invention
The invention relates to devices for preventing overloads and, more particularly, to an automation device having a plurality of modules, where at least one first module is configured to supply the other modules with electrical power and a second module is configured to determine the total power requirement of the automation device, and where the second module determines the total power requirement from the information relating to the power requirement of a respective module, which information is stored in the other modules, compares the power requirement with a threshold value and initiates measures for reducing the power requirement of at least one of the other modules based on the comparison result.
2. Description of the Related Art
Siemens catalog ST PCS 7, chapter 6, February 2010 edition, discloses an automation device having a plurality of modules implemented as subassemblies arranged on a carrier, which each have a printed circuit board provided with electrical and electronic components inside a housing capsule. These components are cooled substantially by convection such that air flows through an opening on the underside of the housing capsule, flows across the components and finally flows through an opening on the top side of the housing capsule, where the air flowing through the housing removes heat from the components. On account of subassemblies designed in this manner, sufficient cooling is possible only when the carrier is arranged horizontally and the subassemblies are arranged vertically on the carrier.
EP 2 073 618 A1 discloses an arrangement in which the heat respectively produced in the subassemblies is supplied to a part on the rear side of a carrier, which part is angled through 90°, via thermally conductive contact-making means to improve the convection in an automation device. This angled part, which extends over the entire length of the carrier, is provided as a heat sink on which air ducts that are provided with a square cross section and comprise a material that does not store heat are arranged, thus achieving a substantially laminar air flow in the air ducts, avoiding turbulence in the air ducts and achieving a very high air throughput in the air ducts and very good heat dissipation. Even with an automation device designed in this manner, sufficient cooling is possible only when the carrier is arranged horizontally in a switchgear cabinet, for example.
A user generally decides, when planning such automation devices, which power supply subassembly is suitable for the subassemblies needed to solve an automation problem so that these subassemblies, for example, subassemblies comprising CPU subassemblies, communication subassemblies, input/output subassemblies or other subassemblies suitable for the automation device, can be sufficiently supplied with the corresponding electrical power even at full load. Here, planning software uses subassembly-specific information to check whether the required expansion of the automation device is permissible at all with regard to the number of subassemblies required and the power requirement thereof, with regard to the respective power loss of the subassemblies to be vertically installed and with regard to a maximum permissible ambient temperature at the place of use. If the expansion is permissible, the planning operation with respect to power balancing is concluded.
When starting up the planned automation device or when changing the planned hardware configuration, the CPU subassembly initially checks, before the actual control mode for solving the automation problem, whether the maximum electrical power which can be provided by the planned power supply subassembly at full load also actually suffices to sufficiently supply the subassemblies. For this purpose, the CPU subassembly reads the information relating to the respective power requirement or the respective power consumption of the subassemblies, which information is stored in the subassemblies, and uses this information to calculate the total power requirement of the automation device. In addition, the CPU subassembly reads the information relating to the maximum current output or the maximum power that can be provided by the power supply subassembly, which information is stored in the power supply subassembly, and compares this power with the total power requirement of the automation device. If the total power requirement exceeds the maximum power, the CPU subassembly prevents the automation device from “running up” and adopting the control mode (“RUN” operating state) or deactivates at least one subassembly that thus does not participate in the control mode. If the automation device has a plurality of power supply subassemblies, the CPU subassembly naturally determines the maximum possible total power output from the information relating to the maximum power output of the respective power supply subassembly, where the information is stored in each power supply subassembly.
As already mentioned, however, fault-free operation of the planned automation device at full load is ensured only when sufficient heat dissipation is ensured. As a result, on account of the structural design of conventional automation devices, the carrier must be mounted horizontally and the subassemblies must be mounted vertically in a switchgear cabinet, or positioned or arranged at another suitable erection site. If a user arranges the subassemblies horizontally in a switchgear cabinet, sufficient heat dissipation is no longer ensured. Consequently, the subassemblies may overheat at full load and may fail.
EP 2 149 956 A1 discloses another conventional automation device. Here, the power supply modules comprising source modules and other modules comprising sink modules are provided with identification means that represent the respective power capacity or power output of the source modules and represent the respective power requirement of the sink modules. On account of these identification means, power balancing is possible both in modules or subassemblies that output current and in modules or subassemblies that draw current. Measures for preventing an overload on account of improper or inappropriate installation in a switchgear cabinet, for example, and resultant reduced air convection are not provided.